The present invention relates to an optical device; and an imaging unit, an imaging apparatus, a radiation image sensor, and a fingerprint identifying apparatus which use the same.
Known as an optical member for transmitting an optical image is one in which a plurality of optical fibers are arranged parallel to each other and integrally formed. Also, an optical device transmitting an optical image while enlarging or reducing it to a given magnification by using two optical members, each of which is mentioned above and has respective end faces cut obliquely and perpendicularly with respect to the optical axis, is disclosed, for example, in U.S. Pat. No. 3,402,000.
However, the above-mentioned optical device has been problematic in that its optical image transmission efficiency is not always sufficient. Therefore, it is an object of the present invention to provide an optical device having a favorable optical image transmission efficiency.
In order to achieve the above-mentioned object, the optical device of the present invention comprises a first optical member, composed of a plurality of optical fibers arranged parallel to each other and integrally formed, having a first entrance surface and a first exit surface which intersect an optical axis at respective angles of xcex11,xcex21; and a second optical member, composed of a plurality of optical fibers arranged parallel to each other and integrally formed, having a second entrance surface and a second exit surface which intersect an optical axis at respective angles of xcex12,xcex22; wherein the first exit surface and the second entrance surface are in contact with each other; wherein the above-mentioned xcex21 is smaller than 90xc2x0; and wherein an angle xcex81 formed between the optical axis of the first optical member and the optical axis of the second optical member is an angle of difference between xcex21 and xcex12.
When xcex21 is made smaller than 90xc2x0, while xcex12 is made smaller than xcex21, and the angle xcex81 formed between the optical axis of the first optical member and the optical axis of the second optical member is set to the angle of difference between xcex21 and xcex12, the angle of refraction in the optical fibers at the joining surface between the first optical member and the second optical member can be lowered, whereby light transmission efficiency can be increased.